UNDER THE WEATHER

Make a simple device to measure the dew point

Suitable For

Grade 8

Difficulty

1

Time Required

<1 Hour

Supervision

Advised

What’s it about?

The ‘dewpoint’ temperature is the temperature at which the air can no longer hold all of its water vapour, and some of the water vapour is forced to condense into liquid water. The dew point is always lower or equal to the ambient air temperature. In the following science experiment, make a simple device for measuring the dew point:

Topics covered

Dew point, Relative humidity

What will I need?

TIN CAN

SPOON

WARM WATER

ICE CUBES

THERMOMETER

Procedure (Method)

Unfortunately, this section is only available in the e-book version of the project.

How does it work?

Unfortunately, this section is only available in the e-book version of the project.

The device built in this science experiment is used to obtain the ‘dew point’ reading. The temperature inside the tin can drops as the ice cubes are added one by one to the warm water, resulting in water vapour to be formed. The water vapour then turned into liquid, called ‘dew’, as it comes in contact with the cold tin can’s surface. At the same time, the air was evaporating the water on the outside of the can, and at the ‘dew point’ evaporation was no longer taking place faster than the rate at which the water was sticking to the can, so it stayed wet. The amount of water vapour in the air determines the temperature at which the water vapour forms on the side of the can. This reading can also tell you the temperature at which dew will form on the grass! (Find out more in the e-book work sheet…)

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